In the field of telecommunications, network operators can provide new kinds of services based on an Advanced Intelligent Network (AIN) architecture, such as the AIN architecture illustrated in FIG. 1.
Local (11, 13, 15 and 17) and/or toll (23, 25 and 31) offices of the public telephone network detect one of a number of call processing events identified as AIN "triggers". An office that detects a trigger will suspend call processing, compile a call data message and forward that message via a common channel interoffice signalling (CCIS) link to an Integrated Service Control Point 40 (ISCP). If needed, the ISCP can instruct the central office to obtain and forward additional information. Once sufficient information about the call has reached the ISCP, the ISCP accesses its stored data tables to translate the received message data into a call control message and returns the call control message to the office of the network via a CCIS link. The network offices then use the call control message to complete the particular call. The AIN architecture permits a wide variety of service features that can be customized to suit the needs of each customer.
In the system shown in FIG. 1, the central office switching systems are Service Switching Points, referred to as SSP's. The SSP can be a tandem switch in the interexchange network or an end office in the Local Exchange Carrier network. SSP's are appropriately equipped programmable switches, programmed to recognize AIN type calls, launch queries to the ISCP and receive commands and data from the ISCP to further process the AIN calls. Such central office switching systems include CCIS communications capabilities. An example of such a switch is a 5ESS type switch manufactured by AT&T; but other vendors, such as Northern Telecom and Seimens, manufacture comparable digital switches which could serve as the SSP's. An ideal implementation would make a variety of Advanced Intelligent Network or AIN type services available at all local central offices throughout the network. Other AIN implementations provide the SSP functionality only at selected points in the network, and end offices without such functionality forward calls to one of the SSP's.
The STPs (e.g. 23, 25 and 31) are packet switching nodes, and the SCPs are data bases of circuit, routing, and customer information.
When the SSP receives a service request from a local end office or a user attached on a direct access line, it formats a service request for the SCP and suspends call processing until it receives a reply. The SSP forwards the request to the STP over e.g. a CCIS link and the STP forwards the request to the NISCP 40.
The STPs are interconnected over a high speed packet network that is heavily protected from failure by alternative paths. STPs are deployed in pairs so that the failure of one system will not affect call processing. STPs pass the call setup request to an SCP over direct circuits or by relaying it to another STP.
The SCP is a high speed database engine that is also deployed in pairs with duplicates of the database. The database has circuit and routing information, and for customers that are connected through a virtual network, the database contains customer information such as class of service, restrictions, and whether the access line is switched or dedicated. The SCP accepts the query from the STP, retrieves the information from the data base, and returns the response over the signalling network. The response generally takes the same route as the original inquiry.
The SSP's 11 and 13 connect to a first local area STP 23, and the SSP's 15 and 17 connect to a second local area STP 25. The connections to the STP's are for signalling purposes. As indicated by the black dots below STP's 23 and 25, each local area STP can connect to a large number of the SSP's. The central offices or SSP's are interconnected to each other by trunk circuits (illustrated in FIG. 1 as bold lines) for carrying telephone services.
The local area STP's 23 and 25, and any number of other such local area STP's communicate with a state or regional STP 31. The state or regional STP 31 in turn provides communications with the ISCP 40. The STP hierarchy can be expanded or contracted to as many levels as needed to serve any size area covered by the Advanced Intelligent Network (AIN) and to service any number of stations and central office switches.
The links between the central office switching systems 'and the local area STP's 23 and 25 are typically SS7 (Signalling System 7) type CCIS interoffice data communication channels. The local area STP's are in turn connected to each other and to the regional STP 31 via a packet switched network. The regional STP 31 also communicates with the ISCP 40 via a packet switched network.
The above described data signalling network between the SSP type central offices and the ISCP is preferred, but other signalling networks could be used. For example, instead of the CCIS links, STP's and packet networks, a number of central office switches and an ISCP could be linked for data communication by a token ring network. Also, the SSP capability may not always be available at the local office level, and several other implementations might be used to provide the requisite SSP capability.
The messages transmitted between the SSP's and the ISCP are all formatted in accord with the Transaction Capabilities Applications Protocol (TCAP). The TCAP protocol provides standardized formats for various query and response messages. Each query and response includes data fields for a variety of different pieces of information relating to the current call. For example, an initial TCAP query from the SSP includes, among other data, a "Service Key" which is the calling party's address. TCAP also specifies a standard message response format including routing information, such as primary carrier ID, alternate carrier ID and second alternate carrier ID and a routing number and a destination number. The TCAP specifies a number of additional message formats, for example a format for a subsequent query from the SSP, and formats for "INVOKE" messages for instructing the SSP to play an announcement or to play an announcement and collect digits.
There could be one or more ISCP's per political subdivision such as a state, to avoid overloading existing CCIS data links. Alternatively, the ISCP could be implemented on a LATA by LATA basis or on a regional operating company basis, i.e., one data base for the entire geographic area serviced by one of the Regional Bell Operating Companies. In fact, if federal regulations permitted, the data base service could become nationwide.
As shown in FIG. 1, the ISCP 40 is an integrated system. Among other system components, the ISCP 40 includes a Service Management System (SMS) 41, a Data and Reporting System (D&RS) 45 and the actual database referred to as a Service Control Point (SCP) 43. The ISCP also typically includes a terminal subsystem referred to as a Service Creation Environment or SCE (not shown), for programming the data base in the SCP 43 for the services subscribed to by each individual business customer.
Although shown as telephones in FIG. 1, the subscriber station terminals can comprise any communication device compatible with the line. Where the line is a standard voice grade telephone line, for example, the terminals could include facsimile devices, modems, etc.
Each central office switching system or SSP normally responds to a service request on a local communication line connected thereto, for example an off-hook followed by dialed digit information, to selectively connect the requesting line to another selected local communication line. The connection may be made locally through only the connected central office switching system. For example, for a call from station A to station B the SSP 11 provides the call connection without any connection to another central office. When the called line connects to a distant station, for example, when station A calls station C, the connection is made through the connected central office switching system SSP 11 and at least one other central office switching system SSP 13 through the telephone trunks interconnecting the two central office switches.
In one type of call processing, the central office switching system responds to an off-hook and receives dialed digits from the calling station. The central office switching system analyzes the received digits to determine if the call is local or not. If the called station is local and the call can be completed through the one central office, the central office switching system connects the calling station to the called station. If, however, the called station is not local, the call must be completed through one or more distant central offices and further processing is necessary.
If the call were connected serially through the trunks and appropriate central offices between the caller and the called party using in-band signalling, the trunks would be engaged before a determination is made whether the called line is available or busy. A called line busy condition would unnecessarily tie up limited trunk capacity, a problem which led to the development of the CCIS system.
In the CCIS type call processing, the local central office suspends the call and sends a query message through one or more of the STP's. The query message goes to the central office to which the called station is connected, referred to as the "terminating" central office. For example, for a call from station A to station C, the query would go from originating SSP 11 to terminating SSP 13. The terminating central office determines whether or not the called station is busy. If the called station is busy, the terminating central office so informs the originating central office which in turn provides a busy signal to the calling station. If the called station is not busy, the terminating central office so informs the originating central office. A telephone connection is then constructed via the trunks and central offices of the network between the calling and called stations. The receiving central office then provides a ringing signal to the called station and sends a ringback tone back through the connection to the calling station.
The call processing routines discussed above are similar to those used in existing networks to complete calls between stations. In an AIN type network system, these normal call processing routines would still be executed for completion of calls between customer stations, when call processing does not involve one of the AIN services.
In an AIN type system, such as shown in FIG. 1, certain calls receive specialized AIN type processing under control of data files stored in the SCP database 43 within the ISCP 40. In such a network, the SSP type local offices of the public telephone network detect a call processing event identified as an AIN "trigger". For ordinary telephone service calls, there would be no event to trigger AIN processing; in such cases the local and toll office switches would function normally to process the calls as discussed above, without referring to the SCP database for instructions. An SSP type switching office which detects a trigger, however, will suspend call processing, compile a TCAP formatted call data message and forward that message via common channel interoffice signalling (CCIS) link and STP(s) to the ISCP 40 which includes the SCP database 3. This TCAP query message contains a substantial amount of information, including, for example, data identifying the off-hook line, the number dialed and the current time. Depending on the particular AIN service, the ISCP uses a piece of data from the query message to identify a subscriber and access the subscriber's files. From the accessed data, the ISCP determines what action to take next. If needed, the ISCP can instruct the central office to obtain and forward additional information, e.g., by playing an announcement to receive and collecting dialed digits or to receive voice input. Once sufficient information about the call has reached the ISCP, the ISCP accesses its stored data tables to translate the received message data into a call control message. The call control message may include a substantial variety of information including, for example, a destination number and trunk group selection information. The ISCP 40 returns the call control message to the SSP which initiated the query via CCIS link and the STP(s). The SSP then uses the call control message to complete the particular call through the network.
FIG. 2 shows in somewhat more detail a typical central office switching system such as those labeled SSP in FIG. 1. In such a switch, line interface modules provide the interface between a time multiplex switch 57 and the physical wiring plant connecting individual subscribers to the central office. The administrative module 55 contains a processor 61 along with program storage 69, call storage 67 and general storage 63. I/O processor 65 interfaces terminals 66 by which operational personnel can administer the system and by which the various operational systems associated with running a network can gain access to the switch and the information contained therein. CCIS terminal 73 and data unit 71 provide an interface to the CCIS network as described above. Message switch 59 links the time multiplex switch 57 and the various control lines with the administrative module processor 61.
In the course of business, the network operator must frequently handle requests from customers or potential customers, such as requests to provide new service, changes to existing service, disconnection of service and transfer and forward of service from one location to another. FIG. 3 illustrates how this is done conventionally. The customer places a call to the business office of the network operator, which call is routed through a switch 310 to an automatic call distributor 320 (which may be a software service provided by the switch) where the call is queued, if necessary, to await the availability of the next Business Office Representative or operator. When a Business Office Representative becomes available, the call is completed to a telephone at that representative's location. The representative inquires as to the nature of the transaction required to assist the calling customer. Typically, when the Business Office Representative determines the identity of the calling party, or the location with respect to which the request for service is directed, the Business Office Representative will access a computer terminal, also at the representative's location, to access data bases containing information about service location and capabilities and customer accounts. The representative will eventually generate a service order to accommodate the request(s) of the calling customer.
FIG. 4 depicts use of the dialing code 911 which is dedicated to public service emergency numbers such as fire, police and ambulance. The local central office 410 switches a 911 call to a dedicated group of trunks 420 which connects to a Public Safety Answering Point (PSAP) 430. Calls can be routed over the switched network to the PSAP, but as there is a risk that calls may be blocked by normal telephone traffic, dedicated lines are normally used. The PSAP is staffed with personnel who have been trained in emergency call handling procedures. Emergency centers can be classified as Basic 911 (B-911) or Enhanced 911 (E-911). Electromechanical offices can route calls to the PSAP, but most 911 features require stored program central offices.
The telecommunications equipment in a B-911 center can be as simple as key telephone service, or calls can be delivered to an automatic call distributor (ACD).
Emergency operators can be given features that enable them to trace calls and hold up a circuit to re-ring the calling party to obtain more information, but they normally cannot identify the caller.
To provide calling party identification, the network operator or other bureau maintains a data base 440 of calling party information that is furnished to the PSAP if E-911 service is used. Besides the originating telephone number, the data base furnishes name and address, the address of the nearest emergency facility, and identification of which facility has emergency jurisdiction. Besides automatic number and location identification, E-911 provides elective routing, which, for overlapping jurisdictions, routes the call to the appropriate PSAP.
Handling of E-911 calls and calls to the business office, described above, is not always satisfactory. When handling calls to the business office, the customer must wait while the customer service representative looks up the service location, the customer's account information and generates a service order.
Another problem with the prior art described above, is that system users cannot place a call to the business office or to 911 from a "disconnected" telephone. It would be desirable to permit a user to order telephone service from the business office using the existing wiring between the user location and the central office, even when that line has been "disconnected". It would also be desirable to permit such a user of a "disconnected" telephone line to be able to acquire emergency services.